Ian’s Bird of the Week – Black-fronted Tern

To mark the 500th bird of the week, here is a rather special tern from New Zealand, the Black-fronted Tern, which I photographed while on the quest for the very special Black Stilt. The tern is special, as it’s a New Zealand endemic, attractive and, unfortunately, endangered. The first photo shows a bird incubating at a typical nesting site on the gravelly bank of one of the branching – ‘braided’ – rivers in the Waitaki Valley on the South Island.

The second photo shows another incubating bird at the same colony four days earlier, when I found the sole Black Stilt. The plant with the palmate leaves is feral Lupin, one of the threats that this species faces, in this case by encroaching on the nesting sites.

I took these photos from a sufficient distance with a 500mm lens so as not to disturb incubating birds, but like many terns they are quite aggressive and other non-incubating individuals like those in the third and fourth photos showed me how unwelcome I was by flying intimidatingly close to me and calling harshly.

They look very smart in breeding plumage with sharp black caps, bright orange bills and legs, and white cheek stripe and rump contrasting with otherwise grey plumage. They’re quite small, 30cm/12in in length, with, by tern standards, quite short tail streamers. In non-breeding plumage, the cap is grey, streaky and less extensive and the orange of the bill and legs is paler. In the breeding season, this is an inland species, nesting only along the rivers of the South Island, though it used to breed on the North Island. Outside the breeding season, the birds disperse to coastal waters with some reaching Stewart Island in the south and North Island but don’t travel far and have never been recorded in Australia. They feed on small fish invertebrates mostly snatched in flight either from the water surface or the ground – they will follow ploughs – and will also plunge into water to catch fish.

The population is estimated at about 5,000 individuals and declining, hence its endangered status. Main threats to the population are predation by introduced mammals particular stoats and weasels, feral weeds, disturbance by people and stock and hydroelectric schemes. Breeding success appears to be low, but colonies do respond well to conservation measures such as protection of nesting sites, removal of weeds by spraying and provision of artificial nesting sites such as rafts. The Black-fronted is one of two endemic New Zealand terns, the other being the marine White-fronted. It’s considered a close relative of the Roseate Tern is quite abundant and many migrate to southeastern Australia in winter.